The present disclosure relates to a power factor corrector, and more particularly, to a circuit that may decrease a ripple current flowing in a capacitor, extend the lifetime of a capacitor and eventually extend the lifetime of a power factor corrector.
Since in the case of an alternating circuit, the phases of a voltage and a current are not necessarily the same, the product of the voltage and the current does not become power that may be actually used. A ratio of the product of the voltage and the current to effective power that may be actually used is referred to as a power factor. When the power factor is small, there is a loss in transmission power and thus a power factor corrector for preventing it is being widely used in various electronics. Also, many countries demand to install such a power factor corrector.
A charging device for charging a battery for an electric vehicle also needs a power factor corrector. In this case, since the output capacitor of a power factor corrector in the charging device has to smooth ripple power corresponding to two times an input power frequency, a capacitor having a large capacitance should be used. Thus, an electrolytic condenser is mainly used.
In general, the followings are considered in designing the output capacitor of a power factor corrector: firstly, a hold-up time at which output power is maintained even while an AC voltage is not supplied, secondly, a ripple current, and thirdly, the magnitude of a circuit. In general, since in the case of consumer electronics, output power is less than or equal to 500 W and their operations should be ensured even when there is instantaneous interruption, the capacitance of a capacitor is designed to be sufficiently large in consideration of the hold-up time. Thus, the ripple current is not an important consideration in design. However, in the case of an electric vehicle, it is general that there is no requirement for the hold-up time, and the magnitude and lifetime of a circuit are importantly considered. Thus, when designing a power factor corrector used in a charging device for an electric vehicle, the ripple current and the lifetime of a capacitor are top considerations.